Checking the performance of the vacuum booster (Mazda Familia BF)

Press the brake pedal several times with the engine off to create the same pressure in the vacuum booster cavities, close to atmospheric.

Keeping the brake pedal depressed, start the engine. If the vacuum booster is working properly, the brake pedal should "go forward" after the engine starts. Otherwise, check the condition and fastening of the check valve and vacuum hose.

Start the engine, let it run for one or two minutes and stop it.

Press the brake pedal several times with normal force.

If the pedal travel is large when first pressed and decreases with each subsequent press, the vacuum booster is working properly. Otherwise, check the condition and fastening of the check valve and vacuum hose.

Start the engine and press the brake pedal with normal force.

Stop the engine and hold the brake pedal down for approximately 30 seconds.

If the pedal does not fall, then the vacuum booster is working properly. Otherwise, check the condition and fastening of the check valve and vacuum hose.